After tons of searching here and the web in general I only ever saw one of this having been done. It was using an aluminum adapter that someone once sold for $150 and is no longer available.
So I fabbed up one. It was just a piece of 3/16 mild plate with 4 holes and some cutting with an angle grinder. From concept to completion was about 30 minutes.
The mount uses the lower chain roller and sub frame to attach to the bike. It feels quite sturdy and supports be while kicking the bike over.
Total cost was $60 for the kickstand and free for the steel I had laying around. Just thought I would throw out another kickstand option for these older YZ's.